Method of producing ceramic articles



Nov. 25, i947. F. v. WIND ET AL METHOD OF PRODUCING CERAMIC ARTICLESFiled Feb. 28, 1944 H 6H POTEN T/AL 519d M Wind Maii/zewd. Raz'morzaaINVENTORS '4 BY M ATTORNEY Patented Nov. 25, 1947 I p a UNITED STATESPATENT OFFICE METHOD OF PRODUCING CERAMIC ARTICLES Fred V. Wind,Montrose, and Matthew J. Ralmondo, Los Angeles, Calif., assignors toPacific Clay Products, Los Angelcs, Calit, a corporation of CaliforniaApplication February 28, 1944, Serial No. 524,294

4 Claims. (Cl. 25-156),

This invention pertains to methods for manususpensions containing notmore than about 50% facturing ceramic articles such as dinnerware, byweight er water. decorative ware, vases, trays and the like, and Themethod of the present invention further other ceramic objects. Themethods of the presdistinguishes from the prior practices in that thecat invention permit the utilization of highly de- 5 ceramic compositionemployed is disseminated so sirable ceramic compositions which could notbe as to form a mist or fog and the particles of such successfullyemployed in the past and permit the disseminated ceramic composition arethen demanufacture of various formed ceramic objects posited upon aporous matrix. In this manner, rapidly and inexpensively, the finishedobjects the minute particles of ceramic composition are beingcharacterized by great strength, lightness l0 permitted to orientthemselves so as to form a and thinness of wall sections and freedomfrom coherent body or article of extremely thin wall internal strains.thickness. The process of'the present invention The manufacture ofso-called chinaware and permits the production of coherent objects,sumother formed objects from ceramic compositions ciently strong intheir unburned state, to be readhas ordinarily involved the forming ormolding ily handled, even though the walls are only 0.04 of the object.A ceramic object may be molded inch thick. The methods described hereininby pressing (as in the manufacture of tile) or it sure th productionof objects of uniform wall may be formed by spinning a bat of ceramicthickness and such objects need not be subjected composition upon thepotters wheel. A still to the jiggering and finishing operations, whichfurther method of forming objects has involved had been employed in thep t, and as a conthe use of what are known as clay slips," thesesequence of these various factors, the finished obbeing aqueoussuspensions or dispersions of clay jects are free from internal strainsand exhibit compositions. These clay slips were ordinarily extremelyhigh mechanical strength.

poured into plaster molds, the porous plaster ab- A further adaptationof the present invention sorbing the water from the liquid suspensionand also contemplates the use of molds or forms permitting the solids tobe retained upon the which are mad from ceramic composition (ininnersurfaces of the plaster mold. After prestead of plaster of Paris), suchmolds or matrices liminary drying. the clay objects thus formed beinglighter, more easily handled by female were liberated from the molds andoften jiggered workers and exhibiting much longer life.

or contoured to final shape. For example, dinso It is an object of thepresent invention, therener plates have been made by casting from a slipfore, to disclose and provide improved methods of in a plaster of Parismold and then supported procedure for use in the manufacture of ceramicupon a rotating table while a profile tool was objects.

brought into contact with one of the surfaces so A further object of theinvention is to disclose as to impart a desired finished contour orshape 3 and provide a method of depositing finely divided to the stillplastic object. ceramic compositions upon'porous molds whereby Mostforming, casting or jiggering operations thin, coherent and strongobjects, free from inrequire the use of relatively plastic ceramiccomternal strains, may be produced.

positions. The clay slips employed contain high An object of the presentinvention, moreover, proportions of water. Clay compositions or com- 40is to disclose and provide methods of manufacpositions in which clayforms the major inturing vitreous and semi-vitreous ware from shortgredient tenaciously retain water and can be ceramic comp o s dried withdifliculty. Shrinkage problems (both Still another object of theinvention is to produring drying and subsequent burning) are also ducthin wall chinaware and other ceramic obencountered. The usual ceramiccomposition is jects w c n n be Subjected o a Secondary incapable ofproducing a vitreous or semi-vitreous form of finishing operation suchas jiggering, the finished body, while this conditionis substanobjectsbeing provided With Smooth. easily d900- tially essential in chinawareor other ceramic obrated surfaces. jects designed to hold liquids,foods, etc. v These and other objects, uses, advantages and Incontradistinction to the previous practices, characteristics of theinvention will become 9.9- the present invention employs what may beparent to those skilled in the art from the fol. termed a short ceramicbody. this identifying a lowing description when taken in connectionwith body which is not plastic or fat. Moreover, the the accompanyingdrawings, in which certain expreferred compositions of the presentinvention emplary compositions will be specifically referred aresubstantially free from feldspar and contain to. but limited amounts ofclays. Moreover, instead In the drawings: of employing liquid, dilute orthin slips which Fig. 1 is a diagrammatic illustration of an aparepoured into the plaster molds in the form of paratus illustrating onemanner in which the ina continuous liquid, the methods of the presentvention may be carried out. invention employ relatively thickdispersions or Referring to the drawings, there is provided a assua eporous mold or matrix It, shown in section. The upper face ii may beformed to produce an article of an especially designed configuration;that is, the contour of an object to be formed. It is important in thepresent invention that the mold or matrix l constitute an electrode ofan electrostatic field. To this end there may be provided a recess I! inthe bottom of the matrix Ill for receiving an electrode l3 which may beof relatively large area. As will be hereinafter explained, a suitablenozzle ll, made of electrically conductive materiahis provided inconiunction with an apparatus, not shown, for disseminating a raw,moisture-containing, ceramic composition to form a mist through thenozzle It with the view of depositing up n the porous matrix ill theparticles of such composition. In order that the matrix l0 mayconstitute an electrode of an electrostatic field, there is provided asource of power l8, preferably of high potential, direct current, thepositive or anode terminal of the source of power it being connected tothe electrode I: by way of a conductor IS, The negative side of thesource of power I6 is connected to the nozzle II by way of the conductorII. A desired electrostatic field is produced between the matrix l0 andthe nozzle it. Whether or not each particle deposited upon the matrix ischarged with electricity or whether it is the general electrostaticfield that produces the result is not clear. However, experimentationhas conclusively roven that this method of depositing such a compositionin mixed form upon a matrix having a predetermined contour produces acoherent article that may be removed from the matrix, which article maythereafter be burned to maturity.

It is preferable that the matrix contain a large portion of steatite,talc or ,other analogous magnesium silicate, the purpose of which willbe hereafter fully explained.

It has been discovered that ceramic bodies particularly adapted for usein making thin chinaware and the like should contain a large proportionof steatite, talc or other analogous magnesium silicate. It has beendetermined, also, that the talc employed should be dehydrated orcalcined, in part at least, before being incorporated into the ceramicbody. Some clay may be employed in the composition but not as a majoringredient. Small quantities of ball clay or socalled ivory fat clay maybe used with advantage.

Feldspar and kaolinite are not preferred ingredients. Small quantitiesof sodium silicate, barium carbonate, dextrin, soda ash, sodiumcarbonate or other defiocculating agent, stabilizing agent or temporarybinder may also be introduced.

All of the ingredients employed should be reduced to a fine state ofdivision. In actual practice, grinding of the ingredients so as to passa 200 mesh sieve (dry) has been found desirable. Exemplary compositionsare as follows:

In both of the above examples the tale employed was'steatite. Thecalcined talc was calcined in lump or granular form and then finelycrushed. It will be noted that the water content of the compositionsranges from 13% in B to 28% in A. Usually the water content ismaintained between about 12% and 35% of the total, and at no time is itin excess of 45% or 50%. The clay content amounts to between 14% and 15%of the total solids in A and B. Usually the clay content is maintainedbetween 10% and 25% of the total solids (dry basis), the tale comprisingthe major ingredient. Between about 40% and 70% of the total solidscomprise calcined talc. Both of the bodies are distinctly short and bothcan be burned to a maturing temperature of about 2l50-2200 F.

In making chinaware, hotel ware and other ceramic objects, ordinaryplaster of Paris molds may be employed but preferably the molds are madeof a steatite composition which may be similar to that given hereinabovein the examples except that the ingredients need not be ground to thesame extent. Moreover, the ceramic body used in making the moldspreferably contains larger amounts of water so as to produce a moreporous unburned body. The resulting mold or matrix, if made from asteatite composition,

can be provided with walls which are appreciably thinner than the wallsof an ordinary plaster of Paris mold. As a result, the mold is ofmaterially reduced weight and can be handled more quickly and readily.Steatite molds have a very much longer life and may be dried rapidly andrepeatedly at temperatures of 500 F. to 800 F. Surfaces of steatitemolds may be ground or carved to impart fine details to the finishedware. It is to be remembered that the ordinary plaster of Paris mold canonly be employed in the production of a limited number of articles,whereas the steatite molds may be used for thousands of articles beforebeing exhausted.

In carrying out the process of the present invention, a ceramiccomposition of the character described hereinabove is disseminated toform a mist or fog. Spray guns or atomizing nozzles may be used. Sprayor fog may be directed toward the mold or matrix, or a tunnel or chambermay be filled with such fog or mist which then deposits upon the porousmolds contained in such chamher.

It is believed that the dissemination of the ceramic composition into amist or fog imparts a static charge to each of the minute droplets. Whenthese minute particles fall upon the matrix, it may be that cataphoresisand electrical endosmose phenomena take place, permitting the solids toorient themselves and form a dense body while the liquid phase israpidly transferred to the matrix. That denser finished articles areobtained by the process of this invention is readily demonstratable.

It is known that more uniform articles are produced by this process,each article being of uniform thickness and physical characteristics. Itis also definitely known that the articles are formed more quickly; thearticles are capable of being formed and ready for removal from thematrix within a very few minutes, whereas hours are necessary in priorslip-casting methods.

The deposition of the mist or fog upon the matrix may be facilitated bythe use of a high potential electrostatic field in a zone contiguous tothe matrix. The matrix itself may form an electrode, generally theanode. Another electrode or electrodes may be positioned in the vicinityof the matrix. In the event the matrix is charged, it

is only necessaly to disseminate the fog of ceramic composition into thefield caused by the charged surface.

Those skilled in the art will readily adapt the modifications of theLodge-Cottrell process to the process of the present invention, inaccordance with the teachings hereof. It may be noted that fieldsobtained by the use of direct currents at 30,000 and 50,000 volts givegood results, but these examples are not to be construed as limiting inany manner.

An object formed in a mold or matrix by the performance of the methoddescribed, may be removed from its mold within a few minutes. Thispermits large numbers of articles or objects to be made with a smallnumber of molds, and obviates the large storage space which is usuallyallocated to molds containing castings.

The green, unburned articles removed from the molds will be found to beprovided with smooth surfaces, to be of remarkably uniform thickness,and to be fairly dry. The objects are sufficiently strong to be readilyhandled during drying, wiping of edges, placement and stacking in kilns,etc. They may be first subjected to a bisque burn and then to a glostburn. If desired, the green, unburned articles may be coated with adesirable transparent or opaque glaze composition and subjected to asingle burning to mature both body and glaze.

The preferred body compositions for use in this process burn to a lightcolored, almost white and homogeneous body. Their extreme density iswell exemplified by the remarkably low absorption of even the unglazedbisque objects; absorption of less than 0.05% and usually on the orderof 0.003% is obtained. Compressive strengths of 115,000 to 120,000pounds per square inch are obtained; the modulus of rupture of onecomposition was found to be over 19,000 pounds to the square inch (on 3inch centers). The finished objects are highly resistant to chipping andthe methods and compositions described herein are eminently suited forthe manufacture of hotel china, where light weight, negligibleabsorption and high resistance to mechanical and thermal shock aredesirable. Thin walled, glazed articles made by the processes heredescribed, are highly translucent and free from strains andinequalities.

It is to be understood that any type of article or object may be made bythe methods and from the compositions herein described. Numerousmodifications and adaptations are embraced by this invention. Thespecific equipment employed may vary with conditions and the magnitudeof the operations being performed. The spray, fog or mist may be formedb forcing the composition through suitable nozzles either by a directlyapplied pressure or by the use of atomizing air, steam or fluid. Thefineness to which the composition is ground is influenced somewhat bythe nozzles used and the thickness desired in the finished article.Although thin walled articles (0.04 to 0.08 inch) have been specificallymentioned, this is not to be considered as a limitation since objects ofany desired thickness can be successfully made.

All changes, modifications and adaptations coming within the scope ofthe appended claims are embraced thereby.

We claim:

1. In a process of forming ceramic objects, the steps of: disseminatinga raw, moisture-containing ceramic composition to form a mist, anddepositing particles of such disseminated composition upon a porousmatrix having a surface corresponding to contours of an object to beformed, said matrix constituting an electrode of an electro-staticfield, to form a layer of composition on such surface, removing acoherent article from said matrix and burning said article to maturityWithout subjecting the article to jiggering.

2. In a process of forming ceramic objects, the steps of: spraying anaqueous suspension containing ceramic body ingredients in a state offine division to form a mist, and depositing particles of said sprayedsuspension upon a ceramic porous matrix provided with a surface havingcontours corresponding to contours of an object to be formed, saidmatrix constituting an electrode of an electro-static field, to form adense layer of composition on such surface, removing a coherent articleof said ceramic composition from the matrix, and then drying and finallyburning the article to maturity without subjecting the article tojiggering.

3. In a process of producing vitreous ceramic objects having anabsorption of less than 0.05%, the steps of: spraying amoisture-containing ceramic composition to form a mist, the solids insaid composition consisting essentially of raw and calcined steatite inmajor proportion and a minor proportion of clay, said solids being in astate of fine division, depositing particles of such disseminatedcomposition upon a porous matrix having a surface corresponding tocontours of an object to be formed, said matrix constituting anelectrode of an electro-static field, to form a layer of composition onsuch surface, removing a coherent article made from such compositionfrom the matrix, and then drying and finally burning the article tomaturity, without subjecting the article to jiggering.

4. In a process of producing vitreous ceramic objects having anabsorption of less than 0.05%. the steps of: spraying amoisture-containing ceramic composition to form a mist, said compositioncontaining between 12% and 35% by weight of water and between 88% and65% by weight of ceramic body ingredients; depositing particles of suchdisseminated composition upon a porous matrix having a surfacecorresponding to contours of an object to be formed, said matrixconstituting an electrode of an electrostatic field, to form a layer ofcomposition on such surface; removing a coherent article made from suchcomposition from the matrix and then drying and finally burning thearticle to maturity, without subjecting the article to jiggering.

FRED V. WIND. MATTHEW J. RAIMONDO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,997,263 Meissner Apr. 9, 19352,048,651 Norton July 21, 1936 2,213,495 Hagar Sept. 3, 1940 2,270,075Miller Jan. 13, 1942 2,307,698 Melton Jan, 5, 1943 2,334,648 RansburgNov. 16, 1943

